This invention relates to electric-to-pressure converters, more commonly referred to in the art as ‘I/P Converters’, which are pressure control instruments used to provide a fluid, usually compressed air, pressure output that is linearly or otherwise proportional to an electrical input signal.
I/P converters are commonly used in connection with process controls in various applications, for example where an electric signal is utilised to control a diaphragm-actuated pneumatic valve, cylinder, or positioner. To achieve consistency in the control process utilizing the diaphragm-actuated pneumatic valve, cylinder, or positioner, the I/P converter must provide a consistent output pressure for a consistent input electric signal irrespective of variations in the external environmental, for example a temperature variation. Any change from the expected value in the output pressure of the I/P converter, caused by the variation in the external environment, will cause errors and consequently inefficiencies in the control process.
Typical I/P converters commonly found in the marketplace do not have any mechanism to prevent undesirable changes in the output pressure of the converter due to changes in temperature. Patent EP0591925 describes a method for temperature compensating an I/P converter using a microprocessor combined with closed loop electronics. This solution is both costly and complex.